http://www.vintagedrumguide.com/images/catalogs/slingerland/1971-slingerland-snare5.jpg yeah its still in the 1971 catalog as a radio king actually

Well I'm partially right. " Slingerland's most famous product line is the Radio King series of drums. These drums were introduced in 1936-'37, and remained Slingerland's flagship snare drums and drum sets until 1957, when the Radio King model briefly disappeared from the product line. Between 1960 and 1962, Radio Kings were reintroduced and remain the premier product for the Slingerland Drum Company. "

So they did technically stop being produced after 1957. So any snare dated from 1957 to 1960 probably isn't a Radio King.

3 ply and solid shell Rk's are the Norm. Also the shell isn't what defines a Radio King, it's the patent that is applied to the snare bridges.

There has always been 3 ply radio kings, though they are rarer than the 1ply. There were also student model radio kings that were mostly 3ply shells, some solid though. I believe the snare pictured is most likely a student model RK or Hollywood Ace. Solid shells can be found on drums up through the 70s and on various models including the Radio King with the 3pt strainer, the Super Krupa with the Clamshell, early Artist models with the zoomatic, and I've even seen Hollywood Ace models with solid shells. I believe they brought back the single ply RK in the 70s too with a TDR strainer. "Radio King" is just a name that Slingerland attached to many different models. We can debate all day over whether or not its the single ply shell, the extended gates, or combination of the 2 that makes it a "true radio king", but at the end of the day if Slingerland cataloged it as a Radio King that's what its called.

If a drum has "Radio King" stamped in the top hoop, it's considered a Radio King. Three ply or solid makes no difference. Having said that, the '55 and later didnt have stamped hoops (with the exception of a very few made that had stamped Sound King hoops.

Also, in the early 50's, hoop stamping was being gradually stopped and many RK snares had no stamps in their RK hoops.

The Buddy Rich model Radio Kings of the 1930's-40's had no extension brackets. Still 100% Radio King.